1. Field of the Invention
This invention relates to a decoder or verifier for examining an audio recording with respect to the presence of evidence indicating whether the recording had been tampered subsequent to its recording wherein data signals based on characterizing information contained in the recorded speech are recorded with the audio on the recording medium for use in detecting evidence of tampering. The invention is particularly pertinent to the examination of audio recordings wherein the characterizing information is based on zero crossing detection.
There are situations where it is desirable to make a recording of audio information, such as speech or speech plus other audio, which will be played back at a later time with the recording made in a manner such that the authenticity of the recording, if questioned, can be verified electronically using a reasonable amount of electronic circuitry. Recordings made in such a manner have application in fields such as law enforcement, private investigation, journalism, medical, legal and many other similar fields where the authenticity of audio recordings may be questioned at some time.
2. Description of the Prior Art
A tamper protected recording system has been disclosed wherein input audio signals are recorded together with a first data signal that includes characterizing information derived from the input audio signals with a second data signal produced during playback that includes characterizing information of the same type obtained from input audio signals, with such second data signal derived from the recorded input audio signals. The two data signals are compared electronically. If the two data signals fail to provide a high level of comparison, the recording is considered to have been altered.